In the field of electrophotography, with the development of electrophotographic systems, the development of a toner for electrophotography meeting the needs of high-image qualities and speeding-up is in demand.
In order to improve especially thermal properties for meeting the needs of high-image qualities and high speeds, polyester resins of which components are easily adjusted are widely used as resin binders for toners, and further plural resins are tried to used.
For example, Japanese Patent Laid-Open No. 2012-194259 discloses a resin binder for a toner, containing a crystalline polyester obtained by polycondensing an alcohol component containing a linear aliphatic diol having from 2 to 10 carbon atoms, and a carboxylic acid component containing a sebacic acid compound in an amount of from 90.0 to 99.8% by mol, and a 1,9-nonanedicarboxylic acid compound and a 1,10-decanedicarboxylic acid compound in a total amount of from 0.2 to 2.0% by mol, for the purposes of improving low-temperature fusing ability, storage property, and durability.
Also, Japanese Patent Laid-Open No. 2004-280084 discloses a toner for electrostatic image development containing a resin binder and a colorant, wherein the resin binder contains two kinds of resins of which softening points differ by 10° C. or more, wherein a resin having a higher softening point is a polyester obtained by reacting a polyethylene terephthalate or a modified polyethylene terephthalate, an alcohol component, and a carboxylic acid component, or a hybrid resin containing the above polyester as one of the resin components, for the purposes of improving low-temperature fusing ability, offset resistance, durability during high-speed printing.
Japanese Patent Laid-Open No. 2004-126545 (U.S. Patent Application Publication No. 2006/0167214) discloses a resin binder for a toner having a polyester structure, characterized in that the structural unit of bisphenol A is contained in an amount of 1% by mol or less of the structural units derived from all the alcohols, that a content proportion of tin is 5 ppm or less, and that a content proportion of an element such as titanium is from 10 to 1,500 ppm, and further that the polyester is obtained by reacting a polyethylene terephthalate, a polycarboxylic acid, and a polyhydric alcohol in the presence of a titanium catalyst or the like, for the purposes of improving low-temperature fusing ability, offset resistance and anti-smearing property.